Fiber optic ferrule

ABSTRACT

A ferrule connectable to a fiber optic cable having an exposed portion of a length of optical fiber extending from a protective buffer. The ferrule includes a cylindrical body including an optical fiber bore coaxial with the body which extends longitudinally from a proximal end of the body through a distal end portion thereof sized to slidably receive the optical fiber therethrough. The distal end portion is mechanically deformable to frictionally engage the optical fiber within the bore, the distal end being either conically shaped or including an outwardly extending ring resulting in the distal end being a substantially planar surface, whereby a projecting length of the optical fiber extending beyond the distal end may be cleaved in very close proximity to the distal end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.11/593,828 filed Nov. 7, 2006.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to fiber optic connectors and ferrulestherefor and more particularly to an improved ferrule which minimizessubsequent end polishing required after the optical fiber has beenmechanically secured within the ferrule.

2. Description of Related Art

Fiber optic cables are utilized for carrying various forms of signals incountless industrial installations, in equipment and in apparatus, andin consumer and commercial products of all types. Typically, each end ofthe optical fiber held within a deformable ferrule which is securedwithin a connector must be polished in a plane generally orthogonal tothe length of the fiber optic cable for proper signal transmission tooccur with a mating optical fiber element.

To accomplish the polishing of the end of the optical fiber, as well asto provide support structure to effect the mechanical engagement betweenfiber optic cable ends, the fiber optic connector such as that shown inFIGS. 7 and 8 of U.S. Pat. No. 5,305,406 invented by Rondeau andincorporated by reference includes a metallic or deformable ferrule orcore 166 mechanically attached around the optical fiber 168 extendingfrom the buffer 232. The ferrule 168 is secured within the surroundingconnector 162 for additional stabilizing support of the ferrule 168. Anadditional metallic sleeve 230 is also provided to interconnect thedistal portion of the buffer 232 and the proximal end of the ferrule 168as best seen in FIG. 8 of the '406 patent.

Both the '406 patent and U.S. Pat. No. 6,510,271 invented by applicantherein, disclose apparatus and methodology to reduce the amount ofprojecting optical fiber which extends beyond the distal tip of theferrule 168 and to minimize the amount of looseness or side clearancebetween the optical fiber and the distal end portion of the ferrule 168after it has been mechanically crimped or swaged around the opticalfiber to mechanically secure this relationship. Thereafter, a smallamount of the projecting optical fiber and the distal end surface of theferrule is typically polished substantially flat and orthogonal to thelongitudinal axis of the ferrule so as to maximize the signaltransmission between polished end surfaces of adjoining optical fiberconnections. However, alternate polished distal tip ends such asradiused or tapered for specialized situations, are also used.

The current prior art is shown in FIGS. 1 to 11. Referring first toFIGS. 1 to 4, a number of metallic deformable ferrules which are used inconjunction with the method disclosed in the '406 patent are there showngenerally at numerals 1, 1 a, 1 b and 1 c. This type of ferrule has beenutilized for a number of years in standard SMA, ST, SC, and FCconnectors as well as in custom fiber optic connectors. These metallicferrules are normally held at the rear or proximal end portion 9 and 9 cto the body of a connector previously described in FIGS. 7 and 8 of the'406 patent. The connector itself forms no portion of the presentinvention and is being described for reference only.

Each of these ferrules 1, 1 a and 1 b include an elongated cylindricalbody 3, 3 a and 3 b, respectively, each having a hollow cylindricalinterior 10 open at a proximal end thereof to receive an end portion ofthe buffer or protective sheath around the optical fiber or opticalfiber bundle. The exposed optical fiber is inserted through the proximalend 7 of the ferrule body and, with respect to the prior art ferruleembodiment of FIGS. 1 to 3, is passed through the cylindrical cavity 10and is guided by tapered transitional region 11 into and through alongitudinal optical fiber bore 6 to extend longitudinally beyond thedistal end 2.

With respect to the prior art embodiment 1 c of FIG. 4, the opticalfiber bore 6 c extends longitudinally through almost the entire ferrulebody 3 c from the tapered transition 11 a which also defines theproximal opening 7 c of the proximal end portion 9 c to the distal end 2c of the distal end portion 8 c.

After the optical fiber 12 has been inserted through the optical fiberbore 6 as seen in FIG. 5 with the buffer 12 a also inserted fully intothe cylindrical interior 10, an impact forming or an impact swaging tool13 having a truncated conical opening 16 defining a conical or taperedsurface 14 and a longitudinal cylindrical bore 15 is brought togetheragainst the edge 5 of the distal end portion 8 a, 8 b or 8 c of FIGS. 1to 4, to mechanically deform the reduced diameter distal end portion 4so as to mechanically crimp and frictionally engage the optical fiber 12within the deformed bore 6′ in FIG. 6. Note in FIG. 5 that the distalend 2 is initially flat and orthogonal with respect to the longitudinalaxis and bore 6 of the ferrule 50 itself.

In FIG. 6, the tool 13 has been forcibly urged against the outer distalcorner 5 of the now deformed distal end portion 4′ so as to cause inwarddeformation of this region at 17 of the ferrule in compliance againstthe tapered surface 14. Several deformations occur during this impactswaging or impact forming operation, the first of which is that theouter corner 5 are severely deformed inwardly so as to at leastpartially collapse the bore 6′ in the region 18. The deformable materialof the ferrule at deformed surface 17 causes tightening around theoptical fiber 12 in the region 18 to reduce and eliminate any clearancewhich has been pre-established by the sizing between the diameter of theoptical fiber 12 and that of the undeformed bore 6, now 6′ whendeformed. Additionally, the previously flat distal end 2 has now taken adish or crater configuration 19 with the distal end portion of theoptical fiber 12 extending longitudinally therebeyond. Typically, thelength of the optical fiber gripping region 18 is in the range of 0.2mm, creating a frictional resistance to movement of the optical fiber 12in the range of approximately 400 gms.

The depth of the concaved crater 19 as referenced in FIG. 7 is in therange of 0.1 mm and obviously will increase in proportion to the amountof force exerted by tool 13. The excess projection of the optical fiber12 must be removed before the end polishing operation is commenced. Todo this, typically the optical fiber 12 is cleaved at cutting line 20 ain FIG. 7. However, the cleaving operation is typically only able tosever the optical fiber 12 in a range of approximately 0.05 mm at 20 afrom the edges of the crater 19. Thereafter, an end grinding andpolishing operation must reduce the remaining exposed portion of theoptical fiber 20 a in FIG. 8. Manual cleaving or the use of a cleavingdevice such as that shown in the '271 patent may be utilized after theoptical fiber 12 has been cleaved to establish distal end 2 d. Theprojecting small portion of optical fiber 12, along with the crater 19must be ground or sanded and polished down to the bottom of the craterat 21 to create preferably a substantially flat orthogonal surface asbest seen in FIG. 11. During the grinding or sanding and polishingoperation, a lateral force in the direction of the array of arrows shownin FIG. 10 is imposed along the gripping area 18 between the opticalfiber 12 and the deformed bore 6′. As a result, the gripping force ingripping region 18 may be reduced by as much as 50% or more or eventotally lost, rendering the ferrule unusable. Moreover, the overalllength of this gripping region 18 may be reduced if excess material fromthe ferrule as well as the optical fiber 12 is removed inadvertently orcarelessly during this polishing operation. The variables which affectthe overall quality of this gripping force in this prior art arrangementare controlled by the impact of the swaging die process shown in FIG. 6,the reduced diameter of the deformable tip 4, and the angle of theconical surface 14 of the swaging tool 13.

BRIEF SUMMARY OF THE INVENTION

This invention is directed to a ferrule connectable to a fiber opticcable having an exposed portion of a length of optical fiber extendingfrom a protective buffer. The ferrule includes an elongated cylindricalbody having a substantially hollow longitudinally extending cylindricalinterior open at a proximal end thereof adapted in size to receive anend portion of the buffer. An optical fiber bore coaxial with the hollowinterior extends longitudinally through a distal end portion of the bodysized to snugably slidably receive the optical fiber passingtherethrough. The distal end portion is mechanically inwardly deformableto frictionally engage the optical fiber within the bore, the distal endbeing either conically shaped having a cone angle such that the distalend is also deformed into a substantially planar surface or the endportion including an outwardly extending ring whereby a projectinglength of the optical fiber extending beyond the distal end may becleaved in very close proximity to the distal end.

It is therefore an object of this invention to provide a fiber opticferrule with enhanced optical fiber retention characteristics.

Yet another object of this invention to provide a ferrule whichsubstantially reduces the cost of the after-assembly polishing processof the end of the ferrule/optical fiber end configuration.

Still another object of this invention is to provide a fiber opticferrule which, by design choice, facilitates selected location of themechanical gripping force region for enhanced optical fiber retentionwithin the ferrule.

Yet another object of this invention is to provide a fiber optic ferrulewhich is substantially less impervious to loosening of the optical fiberafter mechanical assembly thereof to the ferrule during final endpolishing operations.

And another object of this invention is to provide a fiber optic ferrulewhich, when mechanically deformed to establish permanent connection withan optical fiber therewithin, substantially reduces the projected lengthof the optical fiber remaining for polishing removal after cleaving ofthe excess optical fiber from the distal end of the assembly.

In accordance with these and other objects which will become apparenthereinafter, the instant invention will now be described with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) Prior Art

FIGS. 1 to 4 are longitudinal section views of typical metallicdeformable prior ferrules for use in conjunction with a fiber opticcable.

FIG. 5 is an enlarged exploded view of the distal portion of the priorart ferrule embodiment of FIG. 1 in relation to an impact deforming orswaging tool.

FIG. 6 is a view of FIG. 5 showing the tool after deforming impact withthe distal end of the prior art ferrule.

FIG. 7 is a view of FIG. 6 with the tool removed.

FIG. 8 is a view of FIG. 7 after cleavage of the projected distalportion of the optical fiber.

FIG. 9 is an enlarged view of the distal end portion of FIG. 8.

FIG. 10 is a further enlarged view of FIG. 9 showing the ferrulematerial required to be removed as shaded.

FIG. 11 is a view of FIG. 9 after polishing of the distal end thereofhas been accomplished.

The Instant Invention

FIG. 12 is an enlarged section view of a distal end portion of oneembodiment of the ferrule of the present invention with the fiber opticcable in place ready for assembly.

FIG. 13 is a view of FIG. 12 after mechanical deformation of the distaltip portion around the optical fiber.

FIG. 14 is a view of FIG. 13 after cleavage of the projecting portion ofthe optical fiber beyond the distal end of the ferrule.

FIG. 15 is an enlarged partial section view of the distal tip portion ofanother embodiment of the invention with the optical fiber cable inposition prior to assembly.

FIG. 16 is a view of FIG. 15 showing the deforming tool at the point ofimpact with an outwardly laterally projecting ring or bead formed as apart of the distal tip portion.

FIG. 17 is a view of FIG. 16 at the maximum impact of the deforming toolagainst the distal end portion of the ferrule.

FIG. 18 is an enlarged view of the deformed ferrule and optical fiber ofFIG. 17.

FIG. 19 is a view similar to FIG. 15 of still another embodiment of theinvention.

FIG. 12A is an alternate embodiment of FIG. 12

FIG. 19A is an alternate embodiment of FIG. 19.

FIG. 20 is a section view similar to FIG. 19 showing the deforming toolat the point of impact with an outwardly laterally projecting annularring or bead formed as a part of the distal tip portion.

FIG. 21 is a section view of FIG. 20 at the maximum impact of thedeforming tool against the distal end portion of the ferrule.

FIG. 22 is a view similar to FIG. 15 of still another embodiment of theinvention.

FIG. 23 is a view similar to FIG. 15 showing yet another embodiment ofthe invention.

FIG. 24 is a view similar to FIG. 15 showing yet another embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 12 to 14, the preferred embodiment of theinvention is there shown generally at numeral 110. This ferrule 110includes the elongated cylindrical body having the hollow cylindricalinterior 10 similar to the previously described conventional deformableferrules. This embodiment 110 includes the reduced-in-diameter distalend portion 4 having a longitudinally extending optical fiber bore 6 badapted in size to slidably receive the optical fiber 12 which extendsbeyond the buffer 12 a or the protective sheath of the fiber opticcable. This embodiment 110 also includes a tapered transition zone 11which greatly enhances guiding of the distal tip of the optical fiber 12into and through the optical fiber bore 6 b.

The distal end 22 of the ferrule 110 is uniquely configured initially aswill be described with respect to FIGS. 13 and 14 having a very broadnon-flat conical configuration with a cone angle C generally equal to inthe range of 170°-179°, preferably 174°. As seen in FIG. 13, after themechanical deformation of the distal corners 23 by the utilization ofthe deforming tool (not shown as repetitive) against the undeformeddistal end portion 4, the distal corners 23 thus inwardly deform into atapered truncated cone matching the deforming conical surface of thedeforming tool so that the deformable bore tightly binds against theoptical fiber 12 and in a manner which leaves the distal end 22′ asnearly a flat surface. Then, as seen in FIG. 14, the cleaving of theprotruding portion of the optical fiber 12 is easily accomplished invery close proximity to the distal end 22′, leaving only a very smallexposed optical fiber segment D in the range of just a few micrometersfrom the substantially flat distal end 22′. Thereafter, polishing formaximum signal transmission from cable to cable is easily and quicklyaccomplished.

Referring now to FIG. 12A, an alternate embodiment of that shown in FIG.12 is there shown generally at numeral 115. In this embodiment 115, thefirst variation of shoulders of the reduced diameter distal end portion102 are similar to that described in FIG. 3 at 3 b. Further, thisembodiment which also includes longitudinal bore 6 as previouslydescribed for receiving the optical fiber 12, continues concentricallythrough the entire cylindrical body 104 absent the transition 11 andhollow cylindrical interior 10. By this structure, only the opticalfiber 12 extends through the entire cylindrical body 104.

This embodiment 115 again includes the reduced in diameter distal endportion 102 and the very broad non-flat conical configuration of thedistal end 108 as previously described with respect to FIG. 12.

Referring now to FIGS. 15 to 17, another embodiment of the invention isthere shown generally at numeral 120 and, again, this improved ferrule120 includes the elongated body (not shown) which defines the hollowcylindrical interior 32 for receiving the buffer 12 a, the protrudinglength of optical fiber 12 inserted through the longitudinally extendingoptical fiber bore 38 in a fashion as previously described.

To accomplish the two-fold objectives of the present invention, i.e.,(a) end up with a substantially flat distal end surface 30 after thedeformation of the reduced-in-size distal end portion 24 which (b)tightly secures the optical fiber 12 within the bore 38, a triangular insection outwardly extending preferably annular ring or band 26 isprovided formed preferably as an integral part of the reduced-in-sizedistal end portion 28 of the ferrule 120. Once the buffer 12 a and theoptical fiber 12 are inserted into the ferrule 120 as shown in FIG. 16,the deforming tool 34 with its conically tapered surface 36 is impactedagainst these triangular rings 26 which radially inwardly deform asshown in FIG. 17.

As better seen in FIG. 15, the undeformed triangular band 26 have anoutwardly extending dimension H and an offset from the distal end 30 ofG. By this arrangement as seen in FIG. 18, an inwardly exerted forcedistribution E in the direction of arrows 42 clampingly engage aroundthe cylindrical optical fiber 12 at a spacing from the distal end 30selected by dimension G. Likewise, the degree of compression orretention force 42 exerted to securely retain the optical fiber 12 inthe deformed bore 38′ as determined by the outward protrusion H of thetriangular ring 26 may easily be varied to accomplish a desired level ofoptical fiber retention.

Once the deformation of these triangular ring 26 into the configuration26′ shown in FIGS. 17 and 18 is accomplished, cleavage of the protrudingportion of the optical fiber 12 is accomplished at 40 in very closeproximity to the flat distal end 30, leaving only a minimal amount ofpolishing of the end surface 40, the distal end 30 remainingsubstantially flat and orthogonally oriented to the longitudinal axis ofthe ferrule itself.

It is here noted that the diameter of the bore 38 is generally selectedto be slightly larger than the outside diameter of the optical fiber 12to allow sliding translation installation therebetween and to allow forthe bore deformation to occur into the configuration shown in FIG. 18.

Another embodiment of the invention is shown at numeral 130 in FIGS. 19to 21. In this ferrule embodiment 130, the distal end portion 50includes a tapered portion 52 and a triangular laterally or radiallyoutwardly extending annular ring 54 positioned on the tapered portion 52which is established at a conical angle F of preferably less than 30° ormore preferably in the range of about 20°.

This conical angle F generally is equal to the taper 60 of the deformingtool 58 so as to provide an even more uniform inward deformation of thering 54 as seen in FIG. 21. The deformed triangular ring 54′ and theslightly compressed tapered portion 52′ greatly enhance the strength ofretention of the optical fiber 12 within the compressed and deformedbore 64′ around the optical fiber 12. As in previous embodiment 120,this embodiment 130 also leaves the distal end 56 in a substantiallyflattened configuration and orthogonally oriented to the longitudinalaxis of the ferrule 120 thus facilitating close cleavage of theprotruding portion of the optical fiber 12 and requiring minimalpolishing thereafter for maximum signal transmission.

Referring now to FIG. 19A, an alternate embodiment of 130 is there showngenerally at 135. In this embodiment 135, substantially all of thestructure and description with respect to FIG. 19 is reiterated exceptthat the main cylindrical body 132 is of a diameter substantially equalto that of the beginning diameter of taper 135. A cylindrical bore 142designed and configured to slidably receive the optical fiber 12entirely therethrough is provided in this embodiment 135 and, as withrespect to embodiment 130 in FIG. 19, the distal end 136 is in asubstantially flattened configuration and orthogonally oriented withrespect to the longitudinal axis of the main body 132 thus facilitatingclose cleavage of the protruding portion of the optical fiber 12.

Three additional embodiments of the radially outwardly extending annularring concept of the invention are shown in FIGS. 22, 23 and 24. In FIG.22, this embodiment 140 includes trapezoidally configured radiallyoutwardly extending ring 68 integrally formed with the cylindricalreduced-in-diameter distal portion 66. The smaller length 70 of thedistal portion 66 positioned between the ring 68 and the distal end 72of the ferrule 140 is preselected in longitudinal position so that adesired distribution and location of clamping forces of bore 76 asdescribed in FIG. 18 against the optical fiber 12 is accomplished. As inprevious embodiments, the buffer 12 a is provided for within the hollowcylindrical interior 74.

In FIG. 23, this embodiment 150 includes an orthogonally configuredradially outwardly extending ring 82 formed as a part of thereduced-in-diameter distal portion 80, a small amount of which at 84 isprovided to achieve a particularly desired clamping location anddistribution against the optical fiber 12 when inward deformation of thebore 88 distal end portion and the ring 82 is accomplished. Thecylindrical hollow interior 90, again, accommodates the buffer 12 a.

Lastly, in FIG. 24, a semi-circular in cross section annular ring 94 isprovided which outwardly extends from the distal portion 92 leaving asmall distal portion 96 spaced from the distal end 98. The optical fiber12 extends through the longitudinal bore 100 as previously described insliding fashion so that the deformation of the ring 94 will collapse thebore 100 slightly, resulting in the desired degree and tightnessdistribution of the clamping forces for optical fiber retention.

While the instant invention has been shown and described herein in whatare conceived to be the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of theinvention, which is therefore not to be limited to the details disclosedherein, but is to be afforded the full scope of the claims so as toembrace any and all equivalent apparatus and articles.

1. A ferrule connectable to a fiber optic cable having an exposedportion of a length of optical fiber extending from a protective buffer,comprising: an elongated cylindrical body including a cylindricaloptical fiber bore coaxial extending longitudinally and coaxiallythrough said body and being sized to slidably receive the optical fiberpassing therethrough; a distal end portion of said body tapering fromthat of a main portion of said body and including a radially outwardlyextending ring, said distal end portion being mechanically inwardlydeformable against said ring to frictionally engage said optical fiberwithin said bore, said distal end remaining substantially as a planarsurface transversely oriented to a longitudinal axis of said bodywherein a projecting length of the optical fiber extending beyond saiddistal end may be cleaved in close proximity to said distal end.
 2. Aferrule as set forth in claim 1, wherein: an outer surface of said bodyis substantially straight over an entire length thereof from saidproximal end to said tapering distal end portion.
 3. A ferrule as setforth in claim 1, wherein: said distal end portion is reduced in outerdiameter from that of said main portion.
 4. A ferrule as set forth inclaim 3, further comprising: a tapered hollow transition coaxial with aproximal end of said optical fiber bore, the optical fiber being guidedby said transition into said bore.
 5. A ferrule connectable to a fiberoptic cable having an exposed portion of a length of optical fiberextending from a protective buffer, comprising: an elongated cylindricalbody including a cylindrical optical fiber bore coaxial extendinglongitudinally and coaxially through a distal end portion of said bodyand being sized to slidably receive the optical fiber passing through; aradially outwardly extending ring formed on or attached to an outersurface of said distal end portion, said distal end portion beingmechanically inwardly deformable against said ring to frictionallyengage said optical fiber within said bore, said distal end remainingsubstantially as a planar surface transversely oriented to alongitudinal axis of said body wherein a projecting length of theoptical fiber extending beyond said distal end may be cleaved in closeproximity to said distal end.
 6. A ferrule as set forth in claim 5,wherein: said distal end portion is reduced in outer diameter from thatof said main portion.
 7. A ferrule as set forth in claim 5, wherein: anouter surface of said body is substantially straight over an entirelength thereof from said proximal end to said tapering distal endportion.